1. Field of the Invention
The present invention generally relates to an apparatus such as a camera, and particularly relates to a mechanism for locking a cover of a cartridge compartment of the camera which prevents the cover from being opened when the camera is loaded with a cartridge so that a film of the cartridge is prevented from being exposed to light carelessly.
2. Description of the Related Art
Conventionally, there have been provided various types of locking mechanisms for locking a cover of a film cartridge compartment in order to prevent the cover from unlocking carelessly, as shown in Japanese Laid-Open Patent (Unexamined) Publication Nos. 55-46732 and 54-128732.
According to the invention disclosed in the former Publication, the locking mechanism has a construction in which the spool for winding the film has a small diametric part and in which a lever is mounted in such a way that the lever is biased so that the small diametric part of the spool is pushed by the tip of the lever. With this construction, when the film is wound around the spool through the tip of the lever and the small diametric part of the spool, the lever tilts and the mechanism for opening and closing the cover is locked, moving with the lever.
On the other hand, according to the locking mechanism disclosed in the latter Publication, there is provided a sensor or the like, and the mechanism for opening and closing the cover is locked by employing a magnet or the like when the film is detected by the sensor.
The former locking mechanism, however, has a disadvantage that the cover may not be locked certainly, especially if the film does not have a uniform flexural strength, because as the film is wound around the spool, the film is pressed towards the outer surface of the small diametric part of the spool by the tip of the lever, thus letting the film bend. In addition, the former locking mechanism has another disadvantage in that the film may get scratches on it or it may be difficult to get sufficient flatness in the frame set ready for picture taking is because the film is pressed by the lever. On the other hand, because the latter locking mechanism employs an actuator like a magnet in exclusive use for it in order to lock the cover, such problems as high cost of production and large camera size occur.
In the meanwhile, there has been conventionally proposed a thrust-type of cartridge being constructed so that the film thereof is wound up to the tip of the leader inside the film case when the cartridge is not set inside a camera and that the film is thrust and fed out of the film cartridge by a mechanism, for feeding the film, provided on the side of the camera when the cartridge is set inside the camera, and the film fed therefrom is wound around the spool of the camera. If the camera is of the type in use for the thrust-type of cartridge, it is possible to make the cartridge compartment cover relatively smaller and to provide the cover on either the upper or lower surface of the camera body because the cartridge may be inserted in and taken out of the cartridge compartment in an axial direction of the spool. In this type of camera, if the user opens the cartridge compartment cover and tries to take the film cartridge out of the cartridge compartment by force when the film is fed out of the cartridge, not only is the film exposed to light, but it is also possible that the film will tear and that torn pieces of the film will remain inside the camera. If this happens, since the cartridge compartment cover is small, it is difficult for the user to remove the remains of film from the cartridge compartment, and it may be necessary to repair the camera.
Furthermore, Japanese Laid-Open (Unexamined) Patent Publication No. 3-267933, proposes a thrust-type of cartridge constructed so that a member having an indicator on it is integrally mounted to the cartridge spool and rotates together with it, that marks of "EXPOSED", "UNEXPOSED" or the like which display how the film is used are shown on the cartridge case, and that the indicator points to either of these displaying marks, depending upon the state of the film, by controlling the stopping position of the cartridge spool at the time of rewinding the film. In this type of cartridge, if the cartridge is taken out of the camera before the positioning of the indicator with respect to a predetermined displaying mark is completed, the indicator points to a wrong display mark. In order to prevent this wrong indication, it is preferable to prevent the cartridge compartment cover from opening unnecessarily. That is, in cameras employing the thrust-type of cartridge, it is desirable to prevent the cover from opening unnecessarily.